Renovascular actions of adenosine in the isolated perfused rat kidney: possible underlying mechanisms

We studied the renovascular action of adenosine on isolated perfused rat 10 min after drug injections. Adenosine was applied intraarterially as a single bolus injection in logarithmically increasing doses (0.3-30 microg). Adenosine treatment induced a biphasic vascular-response, namely, an initial vasoconstriction followed by a long-lasting vasodilation. Pretreatment with 0.1. 0.3, or 1.0 mM theophylline or quinidine (2 microg/ml) significantly depressed both components of the adenosine response. The vasoconstrictor response to adenosine was not affected by either 0.5 or 1.0 microg/ml dihydroergocristine. whereas the vasodilatory response was dose-dependently reduced. The biphasic response to adenosine was markedly depressed by 10 microg/ml indomethacin and was augmented by combining this agent with quinidine. We studied the possible roles of the platelet activating factor (PAF) and nitric oxide-cGMP systems in the renovascular actions of adenosine. Tebokan (a PAF antagonist) antagonized both components of the response, but methylene blue (MM) reduced only the pressory part Electron-microscopic examination of kidneys exposed for 15 min to MM showed some acute degenerative alterations and constriction in the glomeruli. From these findings, we conclude that the P1/A1, and P2x purinoceptors, the prostaglandins, PAF, and the NO-cGMP systems have a share in the renovascular actions of adenosine.